Radioactive source comprising a polyamidoxime or a polyhydroxamic acid complexed with a radioactive metal



United States Patent 3,154,499 RADIOACTIVE SQURCE COMPRISING A POLY- AMIDGE OR A PQLYHYDROXAMIC ACID CQMPLEXED WITH A RADIOACTIVE METAL Charles A. Fetscher, Short Hiiis, Ni, assignor to Nopco Chemical (Iompany, Newark, N.J., a corporation of New Jersey No Drawing. Filed Jan. 23, 1961, Ser. No. 83,911 20 Claims. (Cl. 252-3811) The present invention relates to sources of radioactivity. More particularly, the present invention relates to new and improved fuel elements.

It is well known that radiation energy derived from radioactive decay can cause many physical and chemical changes. For instance, radiation energy derived from radioactive sources can cause the polymerization of olefinic oils (see Patent No. 2,350,330, Remy, June 6, 1944), and can catalyze the interaction of nitrogen and oxygen (see Patent No. 2,898,277, Harteck et al., August 4, 1959). Thus, it has been a long standing problem in the art to prepare sources of radiation energy derived from radioactive decay, otherwise known as fuel elements. However, there are many dilficulties which to date have not been successfully overcome with regard to the preparation of fuel elements.

For example, one difficulty encountered in most sources of radiation which are described in the prior art is the difficulty of spreading the energy source over a wide area for intimate contact with the materials to be treated. Harteck and Dondes, Nucleonics 15: No. 8, pp. 94 to 98 (1957), overcome this difficulty by incorporating a radioactive material in a glass melt and then spinning the molten glass into fibers. A gas or liquid passing through a mat of these fibers is very effectively exposed to the energy of the radioactive element. However, these fibers are difficult and dangerous to make. The glass is dangerously radioactive right from the start of its manufacture. There is no possibility of adding the dangerous radioactive material as a simple last step after the difficult mechanical operations. In like manner, Patent No. 1,956,948, Fattinger et al., May 1, 1934, describes the preparation of a radioactive artificial fiber by introducing the radioactive material into a spinning solution and thereafter manufacturing the fiber in the usual manner. Here too, the process is hazardous since the danger due to radioactivity is present even before the fibers are formed. As can be seen from the above disclosures, there has been no way to introduce the radioactive material into the finished fiber as a last step. Moreover, to prepare fibers as indicated above would require extensive and hence expensive shielding means for protecting the operators, etc., from exposure. to radioactivity. Finally, even if the above procedures are followed, the radioactive material is still dispersed throughout its carrier which acts as a shield thus reducing the degree of radiation.

Accordingly, it is an object of the present invention to provide for an improved radioactive source or fuel element and to provide for an improved manner of preparing same.

It is another object to provide for a radioactive source or fuel element which is characterized by being an efficient source of radioactive energy, i.e., very little of the energy is lost due to absorption by the carrier.

Another object is to provide for a radioactive source or fuel element which is versatile and adapted for many uses and can be easily modified structurally.

A still further object is to prepare a radioactive source or fuel element in an improved manner so that radiation hazards are reduced to a minimum and hence necessary safety precautions can be reduced to a minimum.

Other objects will become apparent from the detailed description given hereinafter. It is intended however, that the detailed description and specific examples do not limit the invention, but merely indicate the preferred embodiments thereof since various changes and modifications within the scope of the invention will become apparent to those skilled in the art.

I have discovered that the above and other objects can be carried out in the following manner. Outstanding fuel elements which function as sources of radiation energy derived from the radioactive decay of certain radioactive elements or isotopes are high molecular weight organic polymers containing amidoxime or hydroxamic acid substituents, referred to hereinafter as polyamidoximes and polyhydroxamic acids, which are chelated with a radioactive element or isotope or mixture of radioactive elements or isotopes whether naturally obtained or artificially produced.

In U.S. Serial No. 673,157, Fetscher, filed July 22, 1957, now abandoned, and in copending U.S. Serial No. 815,245, now U.S. Patent No. 3,088,798, Fetscher, and copending U.S. Serial No. 815,246, now U.S. Patent No. 3,088,799, Fetscher, both filed May 25, 1959, I have disclosed the preparation of polyamidoximes as well as their chelation with various polyvalent metal ions including uranium and plutonium. I have also disclosed that polyamidoxime chelated with a radioactive metal isotope, e.g'., U will serve as a highly efficient neutron source,

The outstanding results and advantages which accrue from my fuel element are numerous. The chelating unit, i.e., the amidoxime or hydroxamic acid substituent has a relatively low weight unit and hence has a very high theoretical chelating capacity for elements such as uranium and plutonium. Consequently, the polyamidoxime or polyhydroxamic acid can chelate very large quantities of the desired radioactive material. Furthermore, the polyamidoxime or polyhydroxamic acid can be formed into powders, granules, fibers, filaments, yarns, woven or nonwoven fabrics and the like, all of which are characterized by a very high surface to volume ratio. Since most of the chelating function of the polyamidoxime or polyhydroxamic acid occurs on the surface of the polyamidoxime, most of the theoretical chelating capacity of the polyamidoxime or polyhydroxamic acid can be effectively realized.

Also, as a result of the chelation procedure per se, the amount of chelated element or isotope can be regulated very accurately. That is, from a mere trace of radioactive element or isotope up to about 50% by weight of the polyamidoxime or polyhydroxamic acid can be chelated. This allows for a wide range of useful fuel elements having varying degrees of radiation energy. Such allows for great versatility. Versatility is also enhanced, especially when the fuel elements are in the form of a woven or non-woven fabric. The fabric is quite strong and is easily deformable to yield a variety of structures and shapes. Furthermore, a mass of fibers carrying one or more radioactive materials is readily permeable to gases and liquids which are to be altered by the energy of the radioactive change. When granules are used, they can' be used in slurries or in fluidized bed applications. Thus, my fuel elements can be used as an activated energy source for such diverse processes as sterilization, reactions between chemicals, treatment of humans, etc. Indeed, my fuel element when in the form of a fabric is vastly superior to an extremely thin sheet of, e.g., uranium or uranium oxide. Such a metal or oxide sheet of one of the radioactive elements would be difficult and dangerous to fabricate and would be very feeble.

As a result of the fact that most of the theoretical chelating capacity occurs upon the surface of the polyamidoxime or polyhydroxamic acid structure and hence can be effectively utilized, a most efiicient energy source is provided. This is because there is no external layer or barrier of carrier material to slow down or absorb the radiation, e.g., neutrons, ix-particles and B- and 'y-rays. Thus, the radiation energy is essentially completely available for triggering chemical reactions and the like.

When preparing the fuel elements, all of the processing steps save the last one, i.e., the chelation with the radioactive material, can be carried out with complete freedom from radiation hazards. That is, the preparation of the polyamidoxirne or polyhydroxamic acid, the formation of spheres or the spinning into yarns and even the weaving into a fabric is done prior to any contact with radioactive materials. In the prior art, the preparation of metal or oxide sheets, or of glass or artificial filaments containing the radioactive material requires the presence of the radioactive material practically from the beginning of the process. Such, of course, requires elaborate and expensive precautions regarding the control of radiation. In the preparation of the fuel elements herein, no precautions need even be considered until the polyamidoxime or polyhydroxamic acid has been prepared in its desired shape and is ready for chelation with the radioactive material. Indeed, even the chelation step is straightforward and requires only the simplest of precautions to be taken regarding radiation hazards. That is, the polyamidoxime or polyhydroxamic acid, regardless of its size or shape is merely immersed into a solution containing the radioactive isotope. Note also that the simplicity of the chelation procedure allows for an accurate control of the degree of chelation of the radioactive material. It is only necessary to control the concentration of the solution containing the radioactive material.

Since the critical and definitive group in both the polyamido'xime and polyhydroxamic acid is the oxime group, these compounds can be and are characterized by their oxime nitrogen content. This adequately differentiates these two materials from all others although not so well from each other. However, their conspicuously different metal chelating behavior very clearly distinguishes the two from each other. Thus, the combined tests of oxime nitrogen and color resulting from chelation show first that the critical oxime group is present and second whether the substituent is amidoxime or hydroxamic acid. This is demonstrated below. When polyamidoximes and polyhydroxamic acids are chelated with some of the same metals, different colored chelates or complexes will be formed. Moreover, I have found that although polyamidoximes do not chelate silver, zinc and thorium, the polyhydroxamic acids do. The following table illustrates these differences between polyamidoxime and polyhydroxamic acid chelation.

No chelate formed..." Lemon yellow. Very light pink Strong pink. No chelate formed Yellow.

do Black.

The colors of the copper and iron chelates of the two materials are distinctly different. The chelation by the polyhydroxamic acid of silver, zinc and thorium further demonstrate the ease of differentiating between the polyamidoxime and the polyhydroxamic acid.

Regarding the black chelates of the polyhydroxamic acids with gold and silver, it is possible that the polyhydroxamic acid immediately reduces the silver and gold to black colloidal metal. Even if this is so, the colloidal deposit is embedded into the fiber surface and strongly attached. This can be shown by the fact that the silver and gold cannot be removed from the polyhydroxamic acid by vigorous laundering.

PREPARATION OF THE POLYAMIDOXIMES AND POLYHYDROXAMEC ACIDS The polyamidoximes utilized in the present invention can be prepared in a direct and economical manner. Their preparation is based upon the reaction of a nitrile containing polymer with hydroxylamine at temperatures of between 0 and 100 C. for from about A to 40 hours, in a solvent for hydroxylamine. Solvents such as water and alcohols, e.g., methanol, ethanol, or propanol, are satisfactory. Hydroxylamine, as is well known in the art, is commercially available only in the form of its salts such as hydroxylamine sulfate and hydroxylamine hydrochloride. Hence, it is necessary to neutralize a solution of the salt to a pH of about 7.5 in order to utilize the free base. It is only the free base which reacts with the nitrile substituents.

The polyhydroxamic acids utilized in the present invention are likewise prepared in a direct and economical manner by hydrolyzing the polyamidoximes prepared above, with hydrochloric acid. The hydrochloric acid is used as an aqueous solution varying from 10% by weight of hydrochloric acid up to full concentration, i.e., 37% by weight. The temperature of the hydrochloric acid solution during the conversion of the amidoxime substituents to hydroxamic acid substituents should not exceed 35 to 36 C. The stronger the hydrochloric acid solution, the shorter is the time of treatment and the lower is the temperature of the hydrochloric acid solution.

There are a great many types of nitrile containing resins or polymers which can be used in the present in-- vention to serve as starting materials for the preparation of the polyarnidoximes and polyhydroxamic acids. For example, the largest and most economically feasible group comprise the homopolymers and copolymers of acrylonitrile. In the copolymers, the comonomer may be one or more of the common copolymerizable monomers such as styrene, butadiene, vinyl chloride, etc., including all the monomers which will copolymerize with acrylonitrile. A representative list appears of page 50 of the book The Chemistry of Acrylonitrile by the American Cyanamid Company (1951). The nitrile content essential for the formation of the amidoxime and the polyhydroxarnic acid substituents can arise from other sources beside acrylonitrile. Polymers containing alpha-methacrylonitrile, alpha-ethacrylonitrile, fumaryl dinitrile or vinylidene cyanide or the like are perfectly satisfactory. It is only necessary that the homopolymer or copolymer be water insoluble. It is preferred that the polymer contain at least about 10% by weight of nitrile for optimum effectiveness. Note that 10% by weight of nitrile (CN) is about 20% by weight of nitrile calculated as acrylonitrile. This means that in the case of copolymers of acrylonitrile, the non-nitrile comonomers, one or several, can total as much as by weight of the final resin Weight. Since the homopolymer is completely satisfactory, the comonomer content obviously can be zero. Thus, the composition of the resinous nitrile substrate can be from about 20% to by weight of acrylonitrile or an equivalent weight of another nitrile containing monomer, e.g., alpha-methacrylonitrile, and 80% to 0% of one or more comonomers. By copolymer I mean polymers obtained from the polymerization of acrylonitrile or other nitrile containing monomers with at least one other monomer copolymerizable therewith. Depending upon'the process of polymerization, the copolymer may be characterized as random, alternating, graft or block copolymer. The term polymer as used herein includes both homopolymers and copolymers.

In general, the molecular weight of the polymers from which the polyamidoxime and polyhydroxamic acid is prepared is in no way critical. They merely have to be high enough in molecular weight to be substantially insoluble in water and there is no upper limit. The commercially available acrylonitrile homopolymers and copolymers are all completely satisfactory. To carry out my process, I prefer to use preformed fibers in the form of commercially available synthetic textile materials containing these fibers in their woven or non-woven form.

An additional type of nitrile containing polymer is the natural or synthetic polymer to which acrylonitrile has been added as a side chain on the polymer. Cyanoethylated cellulose as cyanoethylated cotton, cyanoethylated Viscose rayon or cyanoethylated insolubilized polyvinyl alcohol are all perfectly satisfactory for the preparation of the polyamidoximes and polyhydroxamic acids provided that the cyanoethylation is carried out to the extent of at least about 20% by Weight of the polymer calculated as acrylonitrile by weight of nitrile calculated as CN). As is obvious to one skilled in the art, the substrate for the cyanoethylation need not be pure cellulose or pure polyvinyl alcohol. The cellulose can be partially esterified or the like, the polyvinyl alcohol may contain some polyvinyl acetate or other extraneous unit in its structure. In fact, the polyvinyl alcohol must be insolubilized before cyanoethylation to be useful in this process. This is easily accomplished by treatment with formaldehyde or glyoxal or by vigorous heat treatment. It is only necessary that the resin retain enough active hydroxyl sites to permit cyanoethylation to the degree cited. With these material I prefer, also, to use preformed fibers; that is, the commercially available natural or synthetic textile materials in either woven or nonwoven form.

As my examples demonstrate, only a partial conversion of the nitrile groups of nitrile containing polymers to amidoxime groups will occur. It must be appreciated that not all of the nitrile substituents can be converted to amidoxime substituents. The nitrile substituents present in the inner portions of the resin are not exposed to the hydroxylamine reactant. The extent of this conversion as indicated by the quantity of hydroxylamine consumed appears to range from about to about 75%. Closed systems were used to preclude the loss of hydroxylamine and thus the hydroxylamine consumed is a fair measure of the extent of reaction. This means that a 100% polyacrylonitrile resin is converted to a polyamidoxime containing from about 19.8% to about 57% by weight of amidoxime substituent,

calculated as such, based upon the total weight of the resin. However, in experiments with cyanoethylated cotton showing a nitrogen content of only 5% (10% by weight of CN, or 20% by weight as acrylonitrile), in some instances the conversion was as low as 40% and the cotton amidoxime was a perfectly operable fibrous chelator with adequate capacity.

I, then, have prepared resinous polyamidoximes containing from 8.5% to 57% by weight of amidoxime substituents. However, in the case of cyanoethylated cellulose, the practical upper limit is about 6% nitrogen introduced. Hence, if this nitrogen which is about 12% nitrile groups is completely converted to amidoxime, a maximum of about by weight of amidoxime substituents can be introduced into the cellulose polymer. The preceding figures are obviously not absolute limits of operability since samples somewhat lower or somewhat higher in amidoxime content can be prepared and used. Hence, material containing as little as 5.0% or even considerably less, or as much as 60% by weight of amidoxime substituents, depending upon the nature of the polymer, would be operable and within the scope of my invention. However, to assure a material which is not 6 appreciably acid sensitive during its use and regeneration, an amidoxime content of about 5.0% to about 25% by weight is preferred. Of course, if a cross-linked polymer is used, then material containing up to about 60% by weight of amidoxime substituents may be used in contact with acids without fear of acid sensitivity.

The conversion of the polyamidoxime substituents to polyhydroxamic acid substituents is substantially complete. This means that a 100% polyacrylonitrile resin which is converted to a polyamidoxime containing from about 19.8% to about 57% by weight of amidoxime substituents can be converted to a polyhydroxamic acid containing from about 20.1% to about 58% by weight of polyhydroxamic acid substituents,

calculated as such, based on the total weight of the resin. Thus, from polyamidoximes which as indicated above contain from about 5.0% to about 60% by weight of amidoxime substituents, depending upon the nature of the polymer, I can obtain polyhydroxamic acids containing from about 5.1% to about 61% by weight of hydroxamic acid substituents. To assure a material which is not appreciably acid sensitive during its use and regeneration, an amidoxime content of about 5 .0% to about 25% by weight is preferred which means that the polyhydroxamic acid obtained from same will contain from about 5.1% to about 25.5% by Weight of hydroxarnic acid substituents. Therefore, since the molecular weights of the amidoxime and hydroxamic acid substituents are 59 and 60 respectively, i.e., they differ by only one unit, the percent of hydroxamic acid substituents present in the material can for all practical purposes be expressed by the same percents used to express the percent amidoxime which is in the material.

There are many examples of the resinous materials described above available in fibrous form to serve as a substrate for preparing the polyamidoximes and polyhydroxarnic acids. Several so-called acrylic fibers are available in commercial or semi-commercial scale. These are all, save one, based upon acrylonitrile. The exception is based upon vinylidene cyanide and is a perfectly satisfactory alternative. Also, there is the much publi cized cyanoethylated cotton. I have prepared cyanoethylated viscose rayon and also cyanoethyla-ted polyvinyl alcohol fiber from the Japanese insolubilized polyvinyl alcohol fiber, trade-named Kuralon. The fibers listed below are all satisfactory for conversion to fibrous polyamidoximes.

Fiber Manufacturer Treatment, Composition it any Orlon Du Pont de None Acrylonitrile.

Nemours. Acrilan Chemstrand d0 Do. Creslan American d0 -96% Acrylonitrile.

Cyanamid. Zetran Dgw Chemical l0 90%Acrylomtr1le.

o. Verel Tennessee do About 50% Aeryloni- Eastman. trile. Dyne1 Carbide & do 4.0% Aerylonitrile- Carbon Chem. 60% Vinyl Chloride. Darlan B. I Goodrich do 50 Mole percent Vinylidene Cyanide-50 Mole percent Vinyl eetate. Cotton Clyangethy 21.7% Acrylonitrile.

ate Viseose do 26.2% Acrylonitrjle. Kuralon Kurashiki Rayon do 20.4% Aerylomtnle.

The detailed compositions of a few additional and typical acrylonitrile polymers which are satisfactory for the production of the polyamidoximes and polyhydrox- 7 amic acids are listed below. The figures are the percents by weight of each monomer in the polymer.

The procedures for preparing the polyamidoxime and polyhydroxamic acid are very straightforward and it is not necessary to vary them greatly from sample to sample. Other useful polyamidoximes are described in Belgian Patent No. 541,496. The polyarnidoximes described in this patent can of course be converted to polyhydroxamic acids if desired. Finally, it should be understood that the present invention is not limited by the procedures utilized in obtaining the polyamidoximes and the polyhydroxamic acids.

Examples I through XIV are directed to the preparation of polyamidoximes. In these examples, a closed system was used, i.e., the reflux condenser was capped to prevent loss of the volatile hydroxylamine.

Example I AMIDOXIME OF POLYACRYLONITRILE (c IN TABLE ABOVE) 40 grams of powdered polyacrylonitrile were added to 750 cc. of a methanolic solution of hydroxylamine. The solution contained 0.048 g. NH OH per cubic centimeter. The mixture was allowed to reflux for 10 hours then. cooled and the solvent removed by filtration. On a basis of the amount of hydroxylamine which was reacted, about 40% of the acrylonitrile substituents were converted to am idoxime. This is equal to 35.7% a-midoxime based on the final resin weight. This powder, shaken with a dilute solution of copper sulfate immediately discharged the blue color and itself turned a deep green. The residual copper in the solution was determined by analysis to be 0.2 p.p.m. of solution. The powder also strongly chelated uranium and gold. Analysis (gain in weight and ash content) showed that it combined with more than 60% of its weight of uranium.

The amidoxime is a a strongly basic group and this sample of uncross-linked polyacrylonitrile in its finely powdered form was easily and relatively completely converted to a polyamidoxime which was soluble in strong mineral acid. Upon reprecipitation with alkali it seemed to be unchanged in chelating power. This demonstrated that these polya-midoximes are relatively stable chemical entities and can go through this solution and regeneration without chemical breakdown.

Solubility of the polymer in acid would frequently be undesirable but it is easily avoided by moderating the conditions of reaction, e.g., by using a lower temperature, a shorter reaction time, a lower concentration of hydroxylamine, by using a granulated resin rather than a powder (alcohol and water do not swell polyacrylonitrile appreciably and hence hydroxylamine will not penetrate and react with as much polymer as in the case of the powder) or by using a copolymer containing some non-nitrile and therefor non-convertible monomer. A cross-linked copolymer would obviously be satisfactory. The acrylic fibers even when almost 100% homopolymers of acrylonitrile are so highly oriented and impervious to solvents that conversion to the extent of acid solubility is easily avoided.

Example 11 ACRYLONITRILE STYRENE COPOLYMER (RESIN OF B 0F PRECEDING TABLE) A commercially available acrylonitrile-styrene copolymer containing 33% acrylonitrile and 67% styrene by weight was converted to the polyamidoxime as follows: The resin was obtained as cubes about one quarter inch in each dimension. These cubes were crushed in a mortar to about ten mesh size. 25 g. of this granulated resin were added to 500 cc. of an aqueous solution of hydroxylamine and held at C. for 24 hours while being gently agitated. The solution contained 0.06 gram of hydroxylamine per cc. and was prepared by neutralizing an aqueous amount of sodium hydroxide. The sodium sulfate formed remained in the solution. After the 24 hour treatment the granules were removed from the solution, washed with cold water and dried. The hydroxylamine consumed indicated a conversion of about 20% of the nitrile groups and a final amidoxime content of 7.1% by weight of the resin. It successfully extracted the color from dilute solutions of copper-sulfate, uranium acetate and gold chloride.

I have used methanolic solutions of hydroxylarnine for most of my work because methanol is a good solvent for 'hydroxylamine and its salts and because the boiling point of methanol which is 65 C. is a convenient automatic temperature control. I have also used ethanol and isopropanol with equivalent results. Other alcohols may be used but the solubility of hydroxylamine salts rapidly diminishes as the alcohol increases in molecular weight. The reaction seems to be very slightly slower in water but the final product is as good as that formed using alcohol.

Example III ACRYLONITRILE BUTADIENE COPOLYMER (RESIN A 0F PRECEDING TABLE) A commercially available acrylonitrile-butadiene copolymer containing 40% acrylonitrile and 60% butadiene in crumb form was converted to the amidoxime as follows: 25 g. of the soft granular material were heated in 500 cc. of an aqueous solution of hydroxylamine containing 0.04 g. of hydroxylamine per cc. The mixture was held at 55 C. for 24 hours. At the end of this time the resin was removed from the liquid, washed with water and dried. The hydroxylamine consumed indicated a conversion of 25% of the nitrile groups and a final amidoxime content of 10.9% by weight. The resin successfully extracted the color from dilute aqueous solution of copper sulfate, uranium acetate and gold chloride.

The amidoximes of the nitrile containing resins in fibrous form were prepared in a very similar manner except that care had to be exercised to prevent damage to the fibers. Very gentle conditions were necessary with some of the thermoplastic synthetic fibers.

Example IV THE AMIDOXIME OF CYANOETHYLATED COTTON 142 g. of cyanoethylated cotton flannel (5.7% N) were immersed in 1480 cc. of a methanolic solution of hydroxylamine. The solvent was refluxed for 24 hours. The cloth was then removed, washed with water and dried. The cotton was not damaged and essentially unchanged in hand. The hydroxylamine consumed indicated an amidoxime content of 9.3% of the final Weight of the modified cotton. Samples of it removed most of the gold, uranium and copper from dilute solutions of these metals by a simple filtration step. The solutions were merely slowly filtered through the treated cloth.

Example V THE AMIDOXIME OF AN ACRYLIC FIBER (ZEFRAN) 8.6 grams of Zefran fabric (a light weight twill) were mmersed in 376 cc. of a 0.045 g. NH OH/cc. solution 1n methanol. The mixture was refluxed for ten hours. The cloth was then removed, washed with water and dried.

The hydroxylamine consumed indicated an amidoxime content of 9.7% by weight. As with the cotton derivative, this cloth strongly chelated a number of heavy metals.

The following examples, set forth in tabular form, were carried out in the same manner as indicated in the preceding examples. As previously indicated, all preparations were carried out in a closed system.

l other radioactive or non-radioactive materials. Usually there will be a mixture of isotopes of the given element including mixtures resulting from artificial enrichment with the more radioactive or desirable isotope for the purpose desired. From a chemical standpoint, such mixtures behave as a single entity. That is, the polyamidoxime or polyhydroxamic acid will chelate the different Ami- Mole NHQOH 2 Gms. gi g? Ex. Original Fiber Ratio, Gms. Girls. Gone, Time, Temp., Hand NHzOH p u NHzOH/ Fabric NH OH glee. Hours C. Reacted t Fabric g 1 Of the Fiber VI Acrilan 4. 35:1 5. 3 l4 3 .032 1 65 Very s1. stiff 19 8. 0 VII COttOll (print)- 2. 821 64. 0 23 9 035 18 65 dO 3 35 8. 5

cyanoethylated. Creslan 2. 16:1 1. 6 2. 2 023 5 65 S1. stiffening 11 12. 3 D3I1al1 2.011 2.5 4.5 .055 2 25 d0 .19 13.7 DYDBL" 2. 021 8. O 10. 0 023 1. 5 50 38 8. 6 Orlon.- 2. 4:1 3. 6 5. 4; 023 4 65 10.0 VGIGL.-- 2. 0:1 6. 3 7. 88 023 1. 5 50 39 11. U Zefrau .r 4. 0:1 6. 3 l6. 9 Q45 4: 50 34 8. 9 Dynel paper 4. 3:1 6.0 16. 1 042 5 62 No change 29 8. 5

1 A molecular weight of 246 was used for the eyanoetliylated cotton cloth (based on N content of 5.7%).

The acrylic fibers were assumed to be polymers of acrylonitrile and a molecular weight of 53 was used.

2 This involves an excess of HNgOH over the polymer and particularly where part of the polymer is derived from a non-convertible cornonomer.

3 From Reeve Angel & 00., 52 Duane St., N.Y., N.Y.

Examples XV through XVII are directed to the preparation of polyhydroxamic acids from polyamidoximes.

Example XV Zefran amidoxime cloth containing 3.15% by weight.

of oxime nitrogen was immersed for 36 minutes in a 20% HCl solution at a temperature of 36 C. The cloth was thereafter washed several times with water and air dried. The oxime nitrogen content of the resulting hydroxamic acid cloth was found to be 2.93%.

Example XVI Example XVII Acrilan amidoxime cloth containing 3.60% by weight of oxime nitrogen was immersed for 30 minutes in a 20% HCl solution at C. The chelates of this product, as above, showed the behavior of a polyhydroxamic acid. The washed and air dried cloth was white in color and strong. It retained 3.40% oxime nitrogen.

Although I have concentrated my studies on fabrics, I have also studied fibers. I found that the fibers behave exactly as the fabrics made from those fibers. The conversion of the nitrile group to the amidoxime group and the conversion of the amidoxime group to the hydroxamic acid group obviously can be effected in a manner similar to the preceding examples on fibers and yarns, as well as on non-woven fabrics made from these fibers and yarns.

CHELATION TO PREPARE THE FUEL ELEMENT tinuously.

Examples of useful radioactive elements or isotopes are 26 27 46 79 90 92 92 Pu and their natural and/or artificial mixtures with isotopes of the same element to the same degree. Thus, if a polyamidoxime or polyhydroxamic acid is chelated with a solution of uranium salts which is enriched, e.g., to the extent of 5% with U the chelator will chelate the uranium isotopes in the same proportion as they are present in the solution. These radioisotopes are utilized in the form of their polyvalent metal states and hence may exist in several ionic forms.

All of the foregoing radioactive elements or isotopes are chelated by polyhydroxamic acids although certain differences have been observed as has been previously shown. For example, polyhydroxamic acids chelated with iron yields a strong cherry red complex whereas polyamidoximes chelated with iron yields a red-brown colored complex. Polyamidoximes do not chelate silver, zinc and thorium whereas polyhydroxamic acids will.

In chelating the polyamidoxime or polyhydroxamic acid with the radioactive material, an aqueous or nonaqueous solution of the radioactive material is first prepared. The concentration can vary. That is, the concentration of the radioactive materials, is such that the polyarnidoxime or polyhydroxamic acid is chelated with from a trace up to about 50% of its weight of the radioactive material. The extent of chelation is of course a functionof the end use of the fuel element. For example, the concentration of the radioactive material can be adjusted so that from about 1% to 50% by weight of radioactive material, based on the weight of the polyamidoxime or polyhydroxamic acid can be chelated. When maximum capacity is desired, the polyamidoxime or polyhydroxamic acid is soaked in a solution containing a stoichiometric excess of the radioactive material which can possibly be chelated. When less than full chelating capacity is desired, the polyamidoxime or polyhydroxamic acid can be immersed in a less than stoichiometric amount of the radioactive material. For a rapid preparation of a strong radiation source, a moderate excess of the radioactive material should be utilized. In this manner, the polyamidoxime or polyhydroxamic acid is quickly and easily loaded to its maximum capacity. It is clear, of course, that if the nitrile containing polymer has a low degree of conversion of nitrile substituents to amidoxime or hydroxamicacid substituents, then even maximum chelation with the radioactive material will give a fuel element with a low percentage of radioactive material. Thus, in determining the amount of radioactive material to be chelated, it is 1 l necessary to select a polyamidoxime or polyhydroxamic acid having sufficient amidoxime or hydroxamic substituents to chelate the requisite amount of radioactive material.

When chelating the radioactive material by use of the polyamidoxime or polyhydroxamic acid, usually the solution containing the radioactive material must be above a minimum pH which is established for each metal. If not, chelation will not occur. Conversely, a chelated polyamidoxime or polyhydroxamic acid can usually be eluted, i.e., the polyamidoxime or polyhydroxamic acid can be regenerated or freed from the radioactive material, if it is immersed in a solution at a pH below the minimum pH utilized in the initial chelation.

The following table sets forth several radioactive elements with their approximate minimum pH values for their chelation. No maximum pH limit is specified since chelation can be accomplished under alkaline con-.

ditions so long as the ion remains in solution and is not precipitated out of solution, e.g., in the form of its hydroxide. Of course if the radioactive material is to be eluted from the polyamidoxime, these same pH values are controlling, i.e., they represent an approximate maximum value at which the radioactive material can be separated from the polyamidoxime. However, in practice it is preferable to elute at a pH appreciably below the minimum pH value for chelation.

TABLE pH (minimum value for chelation; maximum value for elution) lvfetal I For polyhydroxamic acids only.

By the pH 1 is meant acidic pI-Is which are below a pH of 1 and which are usually not accurately measurable on pH indicators which generally are accurate down to a pH of about 1.

For the purpose of regulating pH during chelation of the radioactive metal and the polyamidoxime or polyhydroxamic acid in order to prepare the fuel element, .or to bring about elution, if desired, I may use any organic or inorganic acid with or without a buffer, in order to achieve the desired pH. The acids may be added per se, or as an aqueous solution thereof. Convenient acids are hydrochloric acid, sulfuric acid, formic acid, oxalic acid, etc. It is, of course, understood that other acids may be used and their selection is obvious to one skilled in the art. The adjustment of the pH of the solution in order to carry out the chelation of the radioactive ion under consideration is, of course, within the skill of the art. In fact, in many instances due to the inherent pH of the solution before bringing it into contact with a solid polyamidoxime or polyhydroxamic acid, the pH is at or above the value set forth for the metal.

I have found that temperatures employed during chelation or elution of the radioactive metal ion are not critical. Since the solid polyamidoxime or polyhydroxamic acid, whether in the form of fibers, fabrics, granules, etc. is stable up to about 125 C., I may use temperatures up to such value. Of course, lower temperatures even down to the freezing point of the solution can be used. In other words, the temperature of the materials which is usually room temperature has been found to be convenient. Of course, in industrial processes the temperature of the liquid bodies which contain the radioactive ions to be chelated can be above or-below room temperature; but,

as stated above, the temperatures are not critical.

1 2 The following examples are directed to the preparation and use of my fuel elements.

Example XVIII 0.1 gram of fibrous polyamidoxime was immersed in a 25 cc. solution containing 0.0132 gram per liter of plutonium Pu nitrate (13.2 ppm.) and 18.9 grams per liter of nitric acid. The pH of the solution was 0.7. The fibrous polyamidoxime chelated 50% of the plutonium in an hour and after standing overnight. The residual solution contained 2.6 ppm. of plutonium which was not chelated. Plutonium as indicated above, appears to behave like the more common noble metals and is chelated even from strong acid solutions.

Example XIX A 4 gram sample of cyanoethylated cotton was immersed for 2 minutes in a 5% by weight solution of m-toluene diisocyanate (80% by weight 2,4-isome-r and 20% by weight 2,6-isomer) in benzene. The resulting cross-linked fabric was then centrifuged, vacuum desiccated and heated at C. for one hour. Then the fabric was Washed with benzene, dried, soaked in water for four hours and finally dried. The total weight gain Was found to be 0.221 gram.

The above cross-linked fabric was heated for 6 hours at 75 C. in an aqueous hydroxylamine solution containing 0.045 gram of hydroxylamine per cc. of water. Thereafter the fabric which was a cross-linked polyamidoxime was water washed and dried.

A sample of the above fabric quantitatively removed the uranium present in an aqueous solution which contained 0.1% by weight of uranium present as uranyl acetate, 2% by weight of sodium present as sodium chloride and 2% by weight of calcium present as calcium chloride. The pH of the solution before treatment with the fabric Was 4. The fabric was subsequently treated with a 1% by weight aqueous solution of hydrochloric acid in order to elute the uranium. No damage of the fabric was observed.

By comparison, a polyamidoxime prepared from cyanoethylated cotton, but not treated with m-toluene diisocyanate in order to introduce cross-linking, rapidly disintegrated and partially dissolved when contacted with the 1% hydrochloric acid solution.

Example XX Zefran hydroxamic acid cloth containing 4.36% by weight of oxime nitrogen was immersed for 3 hours in a uranyl acetate solution containing 0.2% by Weight of uranium. The pH was 4.7. The cloth was Washed and air dried. The orange colored fabric chelated 15% uranium based on the Weight of the cloth.

Example XXI Zefran hydroxamic acid cloth containing 4.36% by Weight of oxime nitrogen was immersed for 3 hours in a uranyl acetate solution containing 1% by weight uranium. The pH of the solution was 4.1. The cloth chelated 32% uranium based on the weight of the fabric.

Example XXII Acrilan hydroxamic acid cloth containing 4.38% by weight of oxime nitrogen was immersed in a solution of uranyl acetate containing 1% by weight uranium for 3 hours. The pH of the solution was 4.1. The fiber picked up 16% uranium based on the weight of the cloth.

13 Example XXIV Zefran hydroxamic acid cloth having 4.36% by weight of oxime nitrogen was immersed for hours in a thorium chloride solution containing 1% by weight thorium. The pH of the solution was 2.5. The cloth was rinsed with water and air dried. The resulting golden yellow colored fabric chelated 11% thorium based on the weight of the cloth.

Example XXV Acrilan hydroxamic acid cloth with a 1.84% by weight oxime nitrogen content was immersed for 5 hours in a solution of thorium chloride containing 1% thorium at pH of 2.5. The cloth picked up 8% thorium based on the weight of the fabric.

As indicated previously, my fuel elements are not only safe to prepare but allow for versatility in that varying quantities of radioactive material can be chelated by the polyamidoxime or polyhydroxamic acid and in that the chelated material can be in the shape of particles, fibers, webs, batts and other structures.

For example, in the preparation of oxides of nitrogen from air or an artificial mixture of nitrogen and oxygen, the air or mixture of gases are pumped, preferably at pressures above atmospheric pressure, through a column which is loaded with a mass of polyamidoxime or polyhydroxamic acid fibers chelated with U to an extent of about 25% by weight of the fiber. The column can be surrounded by a steam jacket or other heating element to provide for elevated temperatures, e.g., of the order of 100 C. to 250 C. When the irradiation is carried out at elevated pressures, pressures of the order of 20 to 30 atmospheres can be used. These pressures are maintained by use of the pump which forces the air or mixture of gases through the column.

Also, hydrogen and nitrogen can be combined, hydrocarbons can be chlorinated with chlorine and olefines polymerized by passing these materials through fibers, granules or fabrics of the radioactive polyamidoxime or polyhydroxamic acid. Bodying of oils and the sterilization of liquids can be achieved by exposure to my fuel elements.

Although I have described a column packed with fibers of polyamidoxime or polyhydroxamic acid chelated with.

U other apparatuses utilizing polyamidoximes and polyhydrox-amic acids chelated with other radioactive materials in various structures can be used depending upon whether gases, liquids or solids are being treated. For example, both liquids and gases can be pumped through columns packed with fibers, filaments or granules of polyamidoxime or polyhydroxamic acid chelated with radioactive materials. A filter press can be dressed with a polyamidoxirne or polyhydroxamic fabric chelated with a radioactive material. Alternatively, fibers or granules of chelated polyamidoxime or polyhydroxamic acid can be introduced into a liquid and slurried. Granules of chelated polyarnidoxime or polyhydroxamic acid can be used in fluidized bed applications.

Thin filaments, threads or gauze of polyamidoxime or polyhydroxamic acid can be chelated with radioactive materials, e.g., with cobalt 60, to an extent of about 3% by weight of the polyamidoxime or polyhydroxamic acid. In this manner, a mildly radioactive product is obtained having therapeutic value.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A radioactive source comprising a solid member selected from the group consisting of a solid polyamidoxime and a solid polyhydroxainic acid complexed with a radioactive metal, with the proviso that when said solid material is solid polyamidoxime said radioactive metal is selected from the group consisting of Fe m; p 1o7; A l95; 232 and p 239 2. A radioactive source comprising solid polyhydroxarnic acid complexed with a radioactive metal, said radio- 14 active metal being present in an amount of from a trace up .to about 50% by weight of said polyhydroxamic acid.

3. The radioactive source of claim 2 in which said radioactive metal is U 4. The radioactive source of claim 2 in which said radioactive metal is Pu 5. The radioactive source of claim 2 in which said radioactive metal is U 6. A radioactive source comprising a solid polyamidoxime complexed with a radioactive metal present in an amount of from a trace up to about 50% by Weight of said polyamidoxime, said radioactive metal being selected from the group consisting of Fe Co Pd A 195; 1 232 and p ma 7. The radioactive source of claim 6 in which said radioactive metal is Pu 8. The radioactive source of claim 6 in which said radioactive metal is Th 9. A radioactive source comprising a solid polymer containing from about 5.0% to 60% by weight of hydroxamic acid substituent complexed with a radioactive metal.

10. A radioactive source comprising a solid high molecular weight organic nitrile containing polymer having .at least some of its nitrile substituents converted to hydroxamic acid substituents, said hydroxamic acid substituents being complexed with a radioactive metal.

11. The radioactive source of claim 10 in which said high molecular weight organic nitrile containing polymer is selected from the group consisting of a polymer of acrylonitrile, a polymer of vinylidene cyanide, cyanoethylated cellulose and derivatives thereof and cyanoethylated polyvinyl alcohol, said polymer having at least some of its nitrile substituents converted to hydroxamic substituents.

12. The radioactive source of claim 11 in which said polymers are crosslinked copoly-mers.

13. The radioactive source of claim 11 in which there is present in said polymer at least 5.0% to about 60% by weight of said substituent.

14. The radioactive source of claim 13 in which said polymer is .a polymer of .acrylonitrile.

15. The radioactive source of claim 14 in which said polymer is a =copolymer of acrylonitrile and contains about 40% by weight of acrylonitrile and 60% by weight of vinyl chloride, some of said acrylonitrile converted to hydroxamic substituents which are present in an amount of 13.7% by weight of said polymer.

16. The radioactive source of claim 14 in which said polymer contains at least 90% nitrile substituents cal culated as a-crylonitrile, some of said nitrile substituents converted to hydroxamic acid substit-uents which are present in an amount of about 8.0% by weight of said polymer.

17. The radioactive source of claim 14 in which said polymer of acrylonitrile is a homopolymer.

18. The radioactive source of claim 14 in which said polymer is the polymerization product of acrylonitrile with at least one other polymerizable unsaturated compound.

19. A radioactive source comprising a solid 'molecu lar Weight organic nitrile containing polymer selected from the group consisting of a polymer of acrylonitrile, a polymer of vinylidene cyanide, cyanoethylated cellulose and derivatives thereof and cyanoethylated polyvinyl alcohol, said polymer having at least some of its nitrile substituen-ts converted to amidoxime substituents, said polymer complexed with a radioactive metal being selected from the group consisting of 1%; oe Pd 79Au 90131 and Pu 20. The radioactive source of claim 19 in which there is present in said polymer about 5.0% to 60% by weight of said substituent.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Shapiro June 5, 1956 Benneville et .al Sept. 1, 1959 So-loway Oct. 20, 1959 Harteck et a1. Mar. 15, 1960 Beerbower et a1. Oct. 4, 1960 Yanko et a1. Feb. 28, 1961 Ffiild Oct.10, 1961 1.6 FOREIGN PATENTS 494,964 Great Britain Nov. 3, 1938 541,504 Belgium Oct. 15, 1955 OTHER REFERENCES Nuoleonics, August 1957, pp. 9093 (copy in Div. 46), Chemistry of the Metal Chel-ate Compounds, pp. 443-469 (1952), P rentice-HalL Inc., N.Y.C. (copy in POSL), Martell.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,154,499 October 27, 1964 Charles A. Petscher It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column-8, line 13, after "aqueous", ;ins ert---- solution of hydroxylamine sulfate with an equivalent column 9, footnote 2, for "HN OH" read NH OH column 10, line 32 for w 2'3 235 n T n L read U Signed and sealed this 15th day of March 1966.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD]. BRENNER Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,154,499 I October 27, 1964 Charles A. Fetscher It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Gol-umnfi, line 13, after "aqueousfi insert 'SO t-iOTI f hydroxylamine sulfate with an equivalent column 9, footnote 2, for "HN OI-I read NH OH column 10, line 32, for

23 235 H T H L read H Signed and sealed this 15th day of March 1966.

(SEAL) Attest:

EENEsT W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents 

1. A RADIOACTIVE SOURCE COMPRISING A SOLID MEMBER SELECTED FROM THE GROUP CONSISTING OF A SOLID POLYAMIDOXIME AND A SOLID POLYHYDROXAMIC ACID COMPLEXED WITH A RADIOACTIVE METAL, WITH THE PROVISO THAT WHEN SAID SOLID MATERIAL IS SOLID POLYAMIDOXIME SAID RADIOACTIVE METAL IS SELECTED FROM THE GROUP CONSISTING OF 26FE59; 27CO60; 46PD107; 79AU195; 90TH232 AND 94PU239. 